Tubular void form and voided beam of cementitious material incorporating same



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TUBULAR VOID FORM AND VOIDED BEAM 0F CEMENTITIOUS MATERIAL INCORPORATING SAME Filed Jan. 16, 1967 Sheet 2 of 2 v INVENTOR. H Jam) D. STewARv Fvrro R EQQ United States Patent 3,451,184 TUBULAR VOID FORM AND VOIDED BEAM 0F SEMENTITIOUS MATERIAL INCORPORATING AME John D. Stewart, Sylvania, Ohio, assignor to Owens- Illinois, Inc., a corporation of Ohio Filed Jan. 16, 1967, Ser. No. 609,637

Int. Cl. E04c 3/34 US. Cl. 52-722 8 Claims ABSTRACT OF THE DISCLOSURE This application discloses the construction of a tubular article of generally rectangular cross-section from a unitar sheet of relatively rigid .and inexpensive material, such as corrugated fibreboard or other grade of paperboard, which has utility as a void form in the production of internally voided beams of cementitious material, such as concrete. The tubular void form comprises .an outer wrapper which can be readily manually formed into a self-locking tubular configuration having an internally disposed, longitudinally extending, U-shaped reinforcing rib. The reinforcing rib comprises a multiplicity of spaced, transversely extending slots into which are fitted transversely extending, platelike reinforcing elements which are located internally of the completed void form. A void form of the foregoing type is strong and rigid, being well-suited to support an overlying layer of freshly poured concrete, and can be assembled in a relatively short time without the need for expensive assembly equipment.

Brief summary of the invention In the construction of beams of a cementitious material such as concrete, for example in the construction of reinforced concrete beams, it has long been known that it is advantageous to void the interior of the beams, as the concrete which would otherwise be proximate to the neutral axis of the beam contributes little to the bending strength of the beam and is thereby a liability from the standpoint of cost and weight. Such beams are commonly constructed by pouring fresh concrete into an open-topped outer form to a limited depth in such outer form. At such time, a hollow body or bodies, commonly called void forms, are placed on top of the first concrete layer to cover a predetermined portion or portions of the top surface thereof, after which additional concrete is poured around the void form or forms to flow down to the first pour. Customarily, sufficient additional concrete is poured during the second pour to form a layer of appreciable depth on top of the void form(s). By known techniques, the first and second concrete pours can be combined into a monolithic structure, as by vibrating before either pour has set appreciably, and pre-tensioned steel cables may be incorporated at suitable locations to make the final product a reinforced beam.

Traditionally, void forms for such application have been constructed from metal or wood and have, consequently, been rather expensive. In recent years, however, it has been found that certain grades of paperboard and fibreboard, especially corrugated fibreboard, would be suitable for this use and were relatively inexpensive. The development of thin, effective moisture-impermeable coatings for paper-type products, such as plastic and hot-melt coatings, have upgraded the moisture resistance of such materials to enable them to retain adequate strength in contact with fresh concrete for sufficient time until the concrete has set to a self-supporting, rigid state.

Paper-type void forms heretofore known in the prior art have been difiicult to construct, assemble or erect, frequently involving the need for fastening means such as 3,451,184 Patented June 24, 1969 staples or tape, and have often been of less than staisfactory rigidity or strength. By contrast, void forms in accordance with the present invention have been found to possess good rigidity and strength and possess self-locking characteristics which facilitate their assembly -or erection on a rapid and inexpensive basis.

Accordingly, it is an object of the present invention to provide a tubular article of novel construction which can be formed from a relatively inexpensive paper-type material and which has utility as a void form in the production of a hollow or annular beam of cementitious material.

It is a further object of the present invention to provide such tubular article with self-locking characteristics.

It is also an object of the present invention to provide an internally voided beam of cementitious material permanently comprising an internally disposed tubular void constructed in accordance with the present invention.

For a further understanding of the present invention, attention is directed to the following portion of the specification, the drawing and the appended claims.

In the drawing FIG. 1 is a vertical elevational view, in cross-section, of an internally-voided concrete beam, in accordance with the present invention and incorporating an internally located paperboard type of void form, the concrete beam being shown in the open-topped form in which it was formed;

FIG. 2 is a plan view of a unitary blank of relatively rigid, sheet-like material which is used in the construction of a tubular void form in accordance with the present invention; and

FIGS. 3 and 4 are perspective views showing successive steps in the erection of a void form in accordance with the present invention.

Detailed description of the invention In FIG. 1 there is shown an open-topped concrete form 11 in which an internally voided beam 12 of cementitious material, e.g. concrete, and of rectangular cross-section, has been formed. Beam 12 comprises a generally rectangular void form 13 snugly disposed interiorly thereof, preferably permanently. Thus, the concrete beam 12 may be considered as comprising spaced top and bottom slablike portions 12:: and 12b interconnected by spaced side column-like portions and 12d.

Beam 12 may be formed by pouring a first partial pour of fresh concrete into the bottom of form 11 to a predetermined level in form corresponding to the desired depth of slab-like portion 12b. After the first partial pour has been levelled, and before it has set, void form 13 is placed thereon in a predetermined postion, whereupon a second partial pour of fresh concrete is poured into form 11 filling the spaces between void form 13 and form 11 .and, customarily, to a level overlying the top of void form 13 by an appreciable distance. The juncture between the first and second pours may be caused to become monolithic in nature by vibrating the concrete while the partial pours are still fresh, as is well understood in the art. As is also understood in the art, pretensioned steel cables 14 may be incorporated at predetermined locations of the beam while it is being poured, for exam ple, in slab-like portion 12b of beam 12.

Void form 13 comprises an outer tubular wrapper 15 which may be formed from a blank 16 of relatively rigid sheet-like material, e.g. single-wall, C flute corrugated fibreboard coated, at least on the outer side, with a hotmelt or other moisture impermeable coating material, the liner and facing sheets of such corrugated fibreboard preferably being bonded to one another by means of a resorcinol or other moisture-resistance adhesive. Blank 16 is deformed along a multiplicity of spaced parallel lines 17-24 as by scoring to form a multiplicity of rectangular panels which are foldably connected to one another in a double-ended series.

The series of panesl comprises a major panel 25 extending the full width of the desired form and which constitutes the bottom panel of void form 13 when it is oriented in the direction shown in FIG. 1. (The terms top and bottom are used in this application in a relative sense to correspond to the showing of FIG. 1 and it is not intended to ascribe absolute meanings to these terms.) Disposed on opposite sides of panel 25 are narrow panels 26 and 27 which are folded about score lines 17 and 18 to parallel upstanding positions in relationship to panel 25 and which constitute the side or edge panels of the void form 13.

The top of void form 13 is comprised of first and second top panel portions 28 and 29 which extend inwardly toward one another from edge panels 26 and 27, respectively, being foldably joined to panels 26 and 27 along score lines 19 and 20. Panels 28 and 29 lie in a plane parallel to panel 25 and terminate adjacent one another along a line lying in such plane. It is noted that, for rea sons which will be later apparent, one of panels 28 and 29, shown as panel 28 is approximately twice as wide as the other.

Void form 13, which, in practice, may be of a width of the order of 18 inches, is desirably reinforced by internal means running longitudinally thereof intermediate edge panels 26 and 27 and such means, in the illustrated embodiment, comprises a U-shaped rib 30 formed by first, second and third panels 31-33 of sheet 16 which are joined, in succession, to the longer of the top panel portions, panel 28, along score lines 2123. In the erected void form, panel 32 extends horizontally and lies on top of panel 25, preferably evenly spaced between its edges (score lines 17 and 18), and first and third panels 31 and 33 are disposed in spaced-apart upright positions and serve to transmit loads from the top of void form to the bottom thereof.

Void form 13 is also reinforced by means of a multiplicity of spaced-apart upright plate-like reinforcing elements 34 which extend transversely interiorly of the void form between its edge panels 26 and 27. For void form of 18-inch width, reinforcing elements may, typically, be separated by spacings of the order of inches and may be formed of double-wall corrugated fibreboard for good vertical compressive strength. Reinforcing elements extend between the top and bottom panels of void form 13 and are rapidly assembled with tubular element in selflocking fashion by providing a pair of half-depth slots 35 and 36 in each of elements 34 corresponding to the spacing between panels 31 and 33 of U-shaped rib and by providing a multiplicity of spaced slots 37 in U-shaped rib 30, equal in number to the number of elements 34. Each of slots 37 extends transversely of rib 30 from a point 38 intermediate the vertical edges of panel 31 across panel 32 to a point 39 intermediate the vertical edges of panel 33. In this manner, slots and 36 in each element 34 may be readily engaged in a locking fashion with the portions of slot 37 lying in vertical panels 31 and 33, as is shown more fully in FIG. 3.

The tubular element 15 of void form 13 may be finally closed in self-locking fashion by providing an additional panel or flange 40 which is foldably joined to the other of the top panelportions, panel 29, along score line 24 and which is folded to extend downwardly therefrom to lie adjacent panel 31 of reinforcing rib 30. Panel 40 may be of limited depth, as shown, or it may be of adequate depth to extend all the way to bottom panel 25, in which case its free edge will be provided with a number of transversely extending slots to permit engagement of panel 40 with the slot 35 of each reinforcing element 34.

As a final step in the construction of void form 13, it is preferred to close the open ends thereof to the infiltration of fresh concrete by means of end cap members 41, which may be formed from single-wall corrugated fibreboard, preferably externally coated with a hot-melt or other suitable moisture impermeable coating. While the void form of the illustrated embodiment is of rectangular outline, it is to be understood that the use of a rectangle with one or more rounded or bevelled corners may also be employed within the scope of the present invention, as by the use of closely spaced multiple score lines in place of one or more of score lines 17-20. Thus, the term generally rectangular is intended to encompass such deviations from the outline of a true rectangle.

The best mode known to me to carry out this invention has been described above in terms sufiiciently full, clear, concise and exact as to enable any person skilled in the art to make and use the same. It is to be understood, however, that it is within my contemplation that certain modifications of the above-described mode of practicing the invention can be made by a skilled artisan without departing from the scope of the invention.

I claim:

1. A generally rectangularly-shaped tubular article formed from a unitary sheet of relatively rigid material, said article having utility as a void form in the construction of an annular beam of cementitious material and comprising, in combination: a horizontally disposed rectangular bottom panel extending the full width of said article; first and second upstanding rectangular edge panels foldably joined, respectively, to opposed edges of said bottom panel; first and second top panel portions foldably joined, respectively, to the top edges of the first and second edge panels and extending toward one another in a common plane lying above the bottom panel and parallel thereto, said top panel portions terminating adjacent one another along a line lying in said plane; first, second and third panels foldably joined, in succession, to the terminating edge of one of said top panel portions and forming a U-shaped reinforcing web, the first and third of said panels forming the legs of web and extending vertically between said bottom panel and said one of the top panel portions, and the second of said panels lying on the top of a portion of said bottom panel, said U-shaped web having a plurality of spaced slots extending parallel to one another, each of said slots extending from a point intermediate the vertical edges of said first panel across said second panel to a point intermediate the vertical edges of said third panel; and further comprising a multiplicity of vertically extending reinforcing elements, said reinforcing elements being located in said spaced slots and extending across said article between the first and second edge panels.

2. The structure in accordance with claim 1 wherein each of said reinforcing elements comprises a pair of parallel, vertically extending partial depth slots, said partial depth slots being in engagement with the portions of said spaced slots which are located in said first and third panel portions.

3. The structure in accordance with claim 1 wherein the other of the top panel portions of said tubular article comprises a downwardly vertically extending panel portion lying adjacent the first panel portion of said reinforcing web.

4. The structure in accordance with claim 1 wherein the horizontal width of said one of the to panel portions is approximately twice as great as the horizontal width of the other of the top panel portions.

5. The structure in accordance with claim 1 wherein said beam of cementitious material is rectangular in vertical cross-section and said article is located Within the annulus of said beam.

6. The structure in accordance with claim 2 wherein said beam of cementitious material is rectangular in vertical cross-section and said article is located within the annulus of said beam.

7. The structure in accordance with claim 3 wherein said beam of cementitious material is rectangular in ver- 5 tical cross-section and said article is located within the annulus of said beam.

8. The structure in accordance with claim 4 wherein said beam of cementitious material is rectangular in vertical cross-section and said article is located within the annulus of said beam.

References Cited UNITED STATES PATENTS 2,384,076

Benoit 229-29 Fraber 52577 Nicosia 52577 X Meyer 229-27 5 BOBBY R. GAY, Primary Examiner.

A. M. CALVERT, Assistant Examiner.

9/1945 Cox 229-29 10 22927 US. Cl. X.R. 

